NEW research by academics on Merseyside claims the Black Death was not spread by rats but was a virus which has the potential to re-emerge.

NEW research by academics on Merseyside claims the Black Death was not spread by rats but was a virus which has the potential to re-emerge.

Researchers at Liverpool University have challenged the widely-held view that the plagues, which killed millions of people across Europe in the middle ages, were bubonic plague carried by rats.

A book by Dr Susan Scott and Professor Christopher Duncan suggests the plagues were actually caused by an infectious virus, distantly related to Ebola.

They say the virus was a predecessor to hundreds that are emerging around the world today such as HIV which causes Aids.

And the scientists warn, if this type of plague reappears, the modes of modern transport available and the length of time it takes for symptoms to become apparent would result in high numbers of people succumbing to it.

Prof Duncan, from the university's school of biological sciences, said their research showed bubonic plague could not have been responsible for the plagues which killed approximately 25m people over 300 years from 1347.

He said: "The plagues were probably a viral disease and not a result of bacteria spread by rats. In short, bubonic plague is a disease of rodents and only occasionally does it spread to human beings.

"We had an outbreak in Norwich in the 1920s and it only infected two people."

The study says bubonic plague is prevalent among rats in America but there have been no plagues in humans there since the 19th century.

It also suggests the length of time taken for symptoms to show during the Black Death proves it could not be caused by bubonic plague. Bubonic plague has no quarantine period whereas historical records show people in the middle ages knew their communities were free from the disease after 40 days.

Prof Duncan added: "We have tried to show that it was spread person-to-person and the characteristics of it is such that, when people were infected by plague, there was a 10-day period when nothing happened.

"Then they were infectious for another 22 days. Even in those times of miserable transport, that was long enough for it to spread around and through countries.

"The key factor was the very long period between the point of infection and the symptoms appearing. HIV is one of the only other viruses like that today."

The pair have called the type of plague they have identified haemorrhagic plague to distinguish it from the bubonic strain.

It is also suggested that the virus causing the Black Death probably came from the Levant in the eastern Mediterranean or from Africa where there had been previous examples of the plague.

Professor Duncan said few people today were aware how many plagues are emerging around the world. He cited Ebola and Spanish Flu as examples and pointed to the number of scientists who now travel to the jungles of South America to search for new mutations.

The Liverpool scientists' research concludes the virus causing the Black Death was probably, like Ebola, originally derived from animals. Their book, Biology of Plagues, is published by Cambridge University Press.